1. Field of the Invention
The present invention relates to a thin film transistor (TFT), a method of manufacturing a TFT, a flat panel display (FPD) including the TFT, and a method of manufacturing the FPD. More particularly, the present invention relates to a TFT that includes a semiconductor film that may be simply patterned, a method of manufacturing the TFT, an FPD with the TFT, and a method of manufacturing the FPD.
2. Discussion of the Background
Generally, a TFT may be used in FPDs, such as liquid crystal displays (LCDs), organic electroluminescent (EL) displays, and inorganic EL displays, as a switching device that turns pixels on and off and as a driving device that drives pixels.
A TFT typically includes a semiconductor film, a gate electrode, and source and drain electrodes. The semiconductor film may include heavily doped source and drain regions with a channel region formed therebetween. The gate electrode is electrically insulated from the semiconductor film and located above the channel region. The source and drain electrodes contact the source and drain regions, respectively.
Forming the source and drain electrodes of a metal having a small work function may obtain a smooth flow of charges. However, the metal may have a contact resistance with the semiconductor film, thereby degrading TFT characteristics and increasing power dissipation.
Thus, various methods for lowering this contact resistance have been developed and used. When using an amorphous silicon semiconductor film, an n+silicon film may be interposed between the semiconductor film and the metal source and drain electrodes to attain a smooth flow of electrons or holes. When using polysilicon semiconductor film, the semiconductor film may be doped with impurities to reduce the contact resistance.
A 300° C. or higher temperature may be required to form these conventional structures. However, these temperatures cannot be used with a plastic substrate, which is vulnerable to heat.
Thinner and more flexible FPDs are being manufactured. Much research into the use of plastic substrates is being conducted so that FPDs may be made highly flexible. But as described above, when a plastic substrate is used for a display, high-temperature processes should be avoided. Accordingly, it difficult to use a conventional polysilicon-based TFT.
To solve this problem, organic semiconductors have become more prevalent. An organic semiconductor film may be formed using a low-temperature process, thus enabling the use of organic TFTs.
Nevertheless, the organic semiconductor film cannot be patterned using a conventional patterning process, i.e., a photolithography process. The patterning process may be used to form an active channel, but it typically includes a wet or dry etching process, thus resulting in damage to the organic semiconductor.
Therefore, a new process for patterning semiconductor films is needed.